Sterilization and ligation clips

ABSTRACT

A medical clip ( 10 ) comprising upper and lower jaws and adapted to be latched by latching of the upper jaw ( 14 ) against the lower jaw ( 12 ) in which the upper jaw ( 14 ) is provided with stress relief means.

TECHNICAL FIELD

The present invention relates to medical clips and more particularly tosterilisation or ligation clips suitable for occluding blood vessels.

BACKGROUND OF RELATED ART

Known clips are made from metal upper and lower jaws hinged together,the jaws being hinged to allow the jaws to be opened to encompass a tubeor blood vessel. Usually the jaws are provided with silicon rubberlining. The clip is closed by deformation of the upper jaw which iscurved, the deformation lengthening the upper jaw which is then latchedunder a latch on the lower jaw. Such a clip is described in U.S. Pat.No. 4,489,725 (FILSHIE).

A problem with such clips is that when made of a material such astitanium, the upper jaw or gate is work hardened when initially deformedinto the curved shape.

The consequence of the work hardening of the upper jaw material is thatit requires greater force to overcome the resistance in the materialcaused by such work hardening than is necessary to close the tube orblood vessel structures occluded or ligated by the clip.

This can result in one of two possible malfunctions of the clip.

Firstly, the clip can fail to close even if the correct closure pressureis applied because the upper jaw can spring back because additionalstrength is required to fully lengthen the upper jaw. The clip thereforefails.

The second condition is that sufficient strength is applied tostraighten the upper jaw, but this force has to be greater than isrequired to occlude or ligate. In this case the tube or blood vessel canbe severed creating a possible emergency situation.

SUMMARY

It is an object of the present invention to provide a clip whichobviates the above problem.

The present invention, therefore, provides a medical clip comprisingelongate upper and lower jaws at least said upper jaw being metallic,said lower jaw being hinged by connection to said upper jaw at a firstend of said elongate structure and said lower jaw being formed withlatch means at said other end, said upper jaw being formed curved in anon operated condition and said upper jaw being constructed to bedeformable under applied load to thereby extend the effective length ofsaid upper jaw to enable said upper jaw to latch under said latch meansin said lower jaw when in an operated condition and in which said upperelongate jaw is provided with stress relief means in an intermediatearea along said length of said upper jaw.

Preferably, said stress relief means comprises a hole extending throughsaid upper jaw.

Preferably, both said upper and lower jaws are metallic.

In a preferred embodiment at least one of said jaws is lined internallywith a silicone rubber lining.

More preferably, both said jaws are internally lined with a siliconerubber lining.

In a specific embodiment said upper jaw comprises a first substantiallystraight portion situated at said first end nearest to said hinge, asecond curved portion and a third substantially straight portion, saidthird portion providing a latching surface for engagement with saidlower jaw and in which said hole is formed in said second curvedportion.

In a preferred embodiment, the second curved portion comprises a complexcurvature, including two sections of different radii of curvature.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiment of the present invention will now be described, by way ofexample with reference to the accompanying drawings in which:

FIG. 1 shows a clip according to the present invention in sideelevation,

FIG. 2 shows a perspective view of the clip of FIG. 1,

FIG. 3 shows the clip of FIG. 1 with the silicon rubber lining removed,

FIG. 4 shows the clip of FIG. 3 in plan view,

FIG. 5 shows the clip of FIG. 4 in perspective view,

FIG. 6 shows the lower jaw of the clip in FIG. 3 in side elevation,

FIG. 7 shows the lower jaw in plan view,

FIG. 8 shows the lower jaw in a perspective view,

FIG. 9 shows the upper jaw of the clip of FIG. 3 in side elevation,

FIG. 9a shows a portion of the upper jaw of the clip illustrating analternative form of stress relief,

FIG. 10 shows the upper jaw of FIG. 9 in longitudinal cross section,

FIG. 11 shows the upper jaw of FIG. 9 in plan view, and

FIG. 12 shows a series of hysterisis graphs of force-v-distance fromanvil for a ligation clip according to the present invention with andwithout holes and for a Filshie clip. Hysterisis curve A is for a 0.65mm gate; hysterisis curve B is a 0.5 mm undrilled gate; hysterisis curveC is for a 0.5 mm gate with a 1 mm hole; hysterisis curve D is a 0.5 mmhole and hysterisis curve E is for the known Filshie sterilisation clip.

DETAILED DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

With reference now to FIG. 1, the drawings of the medical clip 10comprises a lower jaw 12 and an upper jaw 14 which are connected by asuitable hinge structure 16.

In this embodiment both upper and lower jaws are provided withrespective silicone rubber linings 140, 120.

With reference to FIG. 3 the clip shown in FIG. 1 is shown without thesilicon rubber linings to illustrate the upper and lower jaw structure.

The lower jaw 12 comprises a generally flat elongate section 122 and alatch portion 124 formed by bending the lower jaw.

The lower jaw comprises two upturned lugs 126, 128 (FIG. 7) which areprovided with holes 130, 132 (only 130 being shown in FIG. 6) whichreceive hinge pins 142, 144 (FIG. 11) found on the upper jaw 14.

The hinge mechanism may be formed by other means not shown and is not acritical feature of the present invention.

The upper jaw 14 shown in greater detail in FIGS. 9 to 11, comprises agenerally curved elongate structure including a first generally straightsection 146, a second generally arcuate section 148, and a thirdgenerally straight section 150.

As seen in FIG. 3, section 150 of upper jaw 14 is designed to engageunder latch member 124 of lower jaw 12 when upper jaw 14 is straightenedby application of force in the direction of arrow 200 which causes theupper jaw 14 to be permanently deformed (straightened) as indicated bydotted line 14′.

As can be seen initially the upper and lower jaws are proportioned suchthat a defined gap G is present in the non operated condition. This gapensures that the clip can be closed from the position shown in FIG. 1 tothe position shown in FIG. 3 without straightening of the upper jaw.

Further movement of the upper jaw in the direction of arrow 200 or 202dependent on the apparatus used for the closure of the clip (see alsoco-pending UK patent application No 9919170.2 multiple application) willcause the upper jaw to be straightened to the position shown at 14′ inwhich the section 150 is forced under the latch 124 thereby permanentlyclosing the clip.

However, if the upper jaw 14 has been work hardened during formation ofthe profile of the upper jaw, the force required in the direction ofarrow 200, 202 will be greater than that required if no work hardeninghas taken place.

This creates two problems, firstly, if not enough force is applied inthe direction of arrow 200 the clip will not latch correctly because theupper jaw 14 will not have been elongated sufficiently to overcome thegap G. The upper jaw because it may have a spring memory may thereforespring back and cause the clip to unlatch even though it appeared tohave been properly latched. Under these circumstances, the clip willtherefore spring open, possibly not immediately dependent on the amountof latching.

Secondly, if too much force is applied in the direction of arrow 200,202 then even though the jaws are silicon lined the force applied to thestructure to be occluded or ligated may be such as to damage orcompletely sever the structure.

Since the clip will possibly still be attached to one part of thestructure the consequences in keyhole type surgery can result inemergency surgery being necessary to remove the clip and repair anydamage.

In accordance with the present invention the necessity to applyexcessive force is avoided by providing stress relief means in the upperjaw.

The stress relief in the example shown in FIGS. 10 and 11 (see also FIG.2) comprises a hole 300 formed through the upper jaw. In this examplethe hole diameter is approximately half the thickness of the width ofthe upper jaw.

The size of the hole can be varied to alter the degree of weakening orstress relief. Alternatively, a lateral groove could be formed in thematerial of the upper jaw to provide the required stress relief. Thedepth of the groove can be adjusted to vary the stress relief. In aspecific example a groove of depth 0.1 mm in an upper jaw for having adepth of 0.65 mm has been found to be effective. Additionally, theposition of the hole and/or groove can be varied to alter thecharacteristics of the upper jaw.

The stress relief could comprise other means such as, for example, anoval hole punched out when the upper jaw curvature is being created.

The stress relief assists in the straightening of the upper jaw tothereby ensure that correct latching of the clip occurs without the useof excessive force applied in the direction of arrow 200.

The upper jaw strength is still sufficient to ensure that the clipremains latched. The use of a central hole provides pressure on theedges of the clip and thereby ensures effective closing pressure on thestructure to be occluded or ligated.

A further possible advantage in the provision of the hole is that it ispossible to injection mould the silicone lining through the hole.

A similar hole could be provided in the lower jaw to allow similarmoulding procedures with the lower jaw.

In a further embodiment illustrated in FIG. 9a the stress relief meanscomprises a notch 141 formed in the upper jaw or gate of the clip. Thenotch 141 may be formed by filing or by stamping which may convenientlybe carried out simultaneously with the curving of the upper jaw.

The size of the notch may be varied to regulate the stress reliefdepending on the thickness and length of the upper jaw.

The following compression tests were carried out on practice clipdesigns.

Compression was applied to the peak of the gate of the clips and thecompression distance measured starting 7 mm above the base of the testerand continuing to 3 mm above the base, when the tester was releasedincrementally until contact with the clip was lost, measuring the forceat a series of points.

Various dimensional checks were made before compression. The finallength of the gate after compression was also measured.

These tests were carried out on the two clips used for the(non-destructive) hardness test. A design modification to weaken afurther clip with 0.65 mm gate was then applied and this was tested.

Results: 0.65 gate, weakened by filing, No 47, 0.65 gate between centreof Clip description 0.5 mm gate as built gate and latch Initial gate14.26 14.28 14.20 length measured vertically from base (mm) Final gatelength 13.71 13.71 13.99 measured in closed clip (mm) Max force, at 5488 82 compression to 3 mm (N) Relaxation of 6 8 8 force with time atcompression to 3 mm, approx. (N) Springback of 0.75 0.75 0.75 centre ofgate after removal of force (mm) Closed clip 3.8 3.78 3.8 height atcentre (mm)

The weakened clip had the shortest initial and the longest final gatelength. This would be expected to lead to much more reliable closure.

The closure force on the 0.5 mm gate Ligation clip is similar to thatfor a Filshie clip—54 N compared to 88 N. This could be useful if it iswished to reduce the force to suite applicator design or the “feel” tothe surgeon.

The closure force on the weakened clip was by comparison much nearer tothe unweakened clip—82 N compared to 88 N. The closure force may prove auseful design and production measure of the amount of weakening applied.

For clips with holes in the upper jaw the following results wereobserved.

Tests were carried out on samples of Ligation Clip with 0.5 mm thickgate, using the compression tester, without silicone rubber samples inthe clips.

The tests were carried out and the results compared to earlier testsdone on Filshie clips and new undrilled Ligation clips with 0.65 and 0.5mm gates with the object of establishing the effect of the holes onclosure force. All these results are shown in the chart shown in FIG.12.

The results show that the holes do not generally affect the closureforce. The results for 1 mm hole show very slightly more force than forthe 1.5 mm hole, as might be expected, but the differences arenegligible and very similar to that for the clips with undrilled 0.5 mmgate.

The weakening of the clip at a point about 5 mm from the latch end ofthe gate increases the latching effectiveness, and the clips tested herelatched well.

These holes, negligibly affect the closure force. This result isconsistent with the fact that the hole is in a part of the clip which isdeliberately formed at a steep angle to the applied force (which isvertically onto the crest of the clip) and may be attributed to theyield 1o occurring over a considerable part of the length of the gate,which is what is needed for the maximum gate extension and optimumlatching. This, if repeatable, is a highly desirable outcome.

What is claimed is:
 1. A medical clip comprising: an upper jaw having afirst end and a second end opposite the first end; a lower jaw having:a.) a first end and a second end opposite the first end; b.) an elongatesection extending from said first end; c.) a latch portion disposed atsaid second end; said first end of said upper jaw being hingedlyconnected to said first end of said lower jaw; a stress relief disposedin said upper jaw in an intermediate area between said first end andsaid second end of said upper jaw; and wherein said upper jaw has afirst curvature in a nonoperated position and wherein said upper jaw isconstructed and arranged to be permanently deformable under an appliedload such that said first curvature is reduced allowing said second endof said upper jaw to latch with said latch portion of said lower jaw inan operated position.
 2. A medical slip as claimed in claim 1, whereinsaid stress relief comprises a hole extending through said upper jaw. 3.A medical clip as claimed in claim 2, wherein said upper jaw includes afirst substantially straight portion situated at said first end nearestto said hinge, a second curved portion and a third substantiallystraight portion, said third portion providing a latching surfaceconstructed and arranged to engage said lower jaw, and wherein said holeis formed in said second curved portion.
 4. A medical clip as claimed inclaim 3, wherein said second curved portion comprises a complexcurvature, including two sections of different radii of curvature.
 5. Amedical clip as claimed in claim 4, wherein said hole has a diameterapproximately half of the width of said upper jaw.
 6. A medical clip asclaimed in claim 1, wherein at least one of said upper and lower jawsare metallic.
 7. A medical clip as claimed in claim 1, wherein at leastone of said upper and lower jaws is lined internally with a siliconerubber lining.
 8. A medical clip as claimed in claim 1, wherein bothsaid upper and lower jaws are internally linked with a silicone rubberlining.
 9. A medical clip as claimed in claim 1, wherein said stressrelief comprises a groove formed in said upper jaw.
 10. A medical clipcomprising: an upper jaw having a first end and a second end oppositethe first end; a lower jaw having: a.) a first end and a second endopposite the first end; b.) an elongate section extending from saidfirst end; c.) a latch portion disposed at said second end; said firstend of said upper jaw being hingedly connected to said first end of saidlower jaw; a stress relief means disposed in said upper jaw in anintermediate area between said first end and said second end of saidupper jaw; and wherein said upper jaw has a first curvature in anonoperated position and wherein said upper jaw is constructed andarranged to be deformable under an applied load such that said firstcurvature is reduced allowing said second end of said upper jaw to latchwith said latch portion of said lower jaw in an operated position.
 11. Amedical slip as claimed in claim 10, wherein said stress relief meanscomprises a hole extending through said upper jaw.
 12. A medical clip asclaimed in claim 11, wherein said upper jaw includes a firstsubstantially straight portion situated at said first end nearest tosaid hinge, a second curved portion and a third substantially straightportion, said third portion providing a latching surface constructed andarranged to engage said lower jaw, and wherein said hole is formed insaid second curved portion.
 13. A medical clip as claimed in claim 12,wherein said second curved portion comprises a complex curvature,including two sections of different radii of curvature.
 14. A medicalclip as claimed in claim 13, wherein said hole has a diameterapproximately half of the width of said upper jaw.
 15. A medical clip asclaimed in claim 10, wherein said stress relief means comprises a grooveformed in said upper jaw.
 16. A medical clip as claimed in claim 10,wherein at least one of said upper and lower jaws are metallic.
 17. Amedical clip as claimed in claim 10, wherein at least one of said upperand lower jaws is lined internally with a silicone rubber lining.
 18. Amedical clip as claimed in claim 10, wherein both said upper and lowerjaws are internally linked with a silicone rubber lining.